Re: [PATCH v5] usb: pci-quirks: always assert xHCI OS ownership

[Mario Limonciello <superm1@kernel.org>]

On 10/15/26 04:17, Michal Pecio wrote:
> On Mon, 12 Oct 2026 15:14:14 -0500, Mario Limonciello wrote:
>> On 9/2/26 00:39, Rishabh Jain wrote:
>>> The xHCI ownership protocol requires the OS driver to assert the HC OS
>>> Owned semaphore before using the host controller, then wait for HC BIOS
>>> Owned to clear if firmware owns it.
>>>
>>> quirk_usb_handoff_xhci() currently asserts OS Owned only when BIOS Owned
>>> is already set. If firmware leaves BIOS Owned clear, Linux uses the xHC
>>> while both ownership semaphores remain clear.
>>>
>>> The timeout fallback also clears BIOS Owned using the original register
>>> value, which can clear OS Owned at the same time.
>>>
>>> On an AMD PROM21 xHCI controller (1022:43fc), this caused every S3
>>> resume to terminate Controller Restore State with USBSTS 0x401. Linux
>>> then reset the host controller, both root hubs and the USB Bluetooth
>>> adapter.
>>>
>>> The controller entered resume ready and halted with USBSTS 0x1.
>>> Endpoint state, 100 ms save/restore delays, scratchpads, the DCBAA,
>>> device contexts and command, event and transfer rings were verified not
>>> to cause the restore error.
>>>
>>> Across four S3 cycles, asserting only HC OS Owned changed USBLEGSUP from
>>> 0x00000801 to 0x01000801 and eliminated the restore failure. Testing
>>> included the unmodified 7.1.8-ogc1.1.fc44.x86_64 distribution kernel
>>> using a test module that set the HC OS Owned semaphore. The same test
>>> was repeated after review with the same result. Clearing USBLEGCTLSTS
>>> was independently verified to be unnecessary.
>>>
>>> Always assert OS Owned for controllers using the standard xHCI handoff,
>>> and leave the existing TI/Renesas forced handoff unchanged. Keep OS
>>> Owned asserted after the standard handoff, including when forcing BIOS
>>> Owned clear after a timeout, to prevent firmware from reclaiming the
>>> controller during subsequent suspends.
>>>
>>> Fixes: 66d4eadd8d06 ("USB: xhci: BIOS handoff and HW initialization.")
>>> Cc: stable@vger.kernel.org
>>> Assisted-by: LLM
>>> Signed-off-by: Rishabh Jain <rishabh.jain1198@gmail.com>
>>> ---
>>
>> Reviewed-by: Mario Limonciello (AMD) <superm1@kernel.org>
> 
> Yes, this fixes a legit issue and would be worth getting in mainline.
> Two users confirmed the patch works for them, though no one could be
> bothered to post proper Tested-by here :(
> 
> https://lore.kernel.org/linux-usb/P1FsfbW--F-9@tuta.io/
> https://lore.kernel.org/linux-usb/CY8PR14MB59803EC0F6C7FD39A6D3C42FA0BF2@CY8PR14MB5980.namprd14.prod.outlook.com/

They're public assertions, let's just put T-b tags for them so b4 can 
pick them up from this thread.

Tested-by: McKenna Fan <blue_sun@tuta.io>
Tested-by: Quinn Schive <quinnschive@hotmail.com>
> 
>>
>>> I kept val unchanged for the error log, restored the original handshake
>>> formatting, and explicitly preserve OS Owned when forcing BIOS Owned
>>> clear after a timeout. Documented timeout issue in commit message.
>>>
>>> I repeated the same S3 test on the unmodified
>>> 7.1.8-ogc1.1.fc44.x86_64 distribution kernel using the test module, with
>>> the same successful result.
>>>
>>> Changes in v5:
>>> - Preserve the original ownership value for error logging.
>>> - Restore the original handshake formatting.
>>> - Explicitly retain OS Owned in the timeout fallback.
>>>
>>>    drivers/usb/host/pci-quirks.c | 13 ++++++++-----
>>>    1 file changed, 8 insertions(+), 5 deletions(-)
>>>
>>> diff --git a/drivers/usb/host/pci-quirks.c b/drivers/usb/host/pci-quirks.c
>>> index 0404489c2f6a..2b12a35e6f10 100644
>>> --- a/drivers/usb/host/pci-quirks.c
>>> +++ b/drivers/usb/host/pci-quirks.c
>>> @@ -1193,10 +1193,11 @@ static void quirk_usb_handoff_xhci(struct pci_dev *pdev)
>>>    			 && pdev->device == 0x0014)) {
>>>    		val = (val | XHCI_HC_OS_OWNED) & ~XHCI_HC_BIOS_OWNED;
>>>    		writel(val, base + ext_cap_offset);
>>> -	}
>>> -
>>> -	/* If the BIOS owns the HC, signal that the OS wants it, and wait */
>>> -	if (val & XHCI_HC_BIOS_OWNED) {
>>> +	} else {
>>> +		/*
>>> +		 * Perform the standard handoff and leave OS ownership set to
>>> +		 * keep the BIOS at bay during subsequent suspends.
>>> +		 */
>>>    		writel(val | XHCI_HC_OS_OWNED, base + ext_cap_offset);
>>>    
>>>    		/* Wait for 1 second with 10 microsecond polling interval */
>>> @@ -1208,7 +1209,9 @@ static void quirk_usb_handoff_xhci(struct pci_dev *pdev)
>>>    			dev_warn(&pdev->dev,
>>>    				 "xHCI BIOS handoff failed (BIOS bug ?) %08x\n",
>>>    				 val);
>>> -			writel(val & ~XHCI_HC_BIOS_OWNED, base + ext_cap_offset);
>>> +			writel((val | XHCI_HC_OS_OWNED) &
>>> +			       ~XHCI_HC_BIOS_OWNED,
>>> +			       base + ext_cap_offset);
>>>    		}
>>>    	}
>>>      
>>